64bit KEY/IV's

[ilovevbclassic]

Hi all,

Just came across this wonderful bit of S/W, and as a hobbiest owner of a paid-for version of VB6; this is quite stunning stuff!

I only find these (deminishing) good-bits for vb6 when I get a problem with some code (which happens quite a lot!...but Google answers less and less).

Basically I want to DES encrypt a file and be able to unencrypt the same file using a KEY of 8 bytes and an IV of 8 bytes, using the file: ..\Examples\Cryptography\FileEncryption\FileEncryption.vbp

I modifiy the KEY or IV to be > four bytes, ie:

mCsp.Key = "12349" ' fails with error dialog:
..."VBCorLib.ArgumentException: Invalid key size.
...
...Parameter Name: key"

but if

mCsp.Key = Chr(&H4) & Chr(&H3) & Chr(&H2) & Chr(&H1) ' seems happy at 32bit

All seems well.

Is there a Unicode thing that I need to alter to allow a 64 bit KEY/IV?...or am I just missing something?

[ilovevbclassic]

This problem had already been discussed and resolved by altering the method used to dimention the KEY & IV byte arrays...should have looked closer before posting.

Here:
killian35.proboards.com/index.cgi?board=Help&action=display&thread=93

[Kelly Ethridge]

Hello there,

The Key and IV properties are byte arrays. By assigning a string value, the string is being implicitly converted to a byte array. The characters are not converted, they are simply copied as their byte values. Each character is 16 bits, so your 4 character string is actual 64 bits, not 32. So that string is successful. Your failing string of 5 digits is actually 80 bits, so it will fail. You should fill an 8 byte array by hand for complete control.

You can use the Rfc2898DeriveBytes class to generate 8 byte arrays from a passphrase instead.


Const SALT_SIZE As Long = 8
Dim Gen As Rfc2898DeriveBytes
Set Gen = Cor.NewRfc2898DeriveBytes("passphrase", SALT_SIZE)

Dim Salt() As Byte
Dim Key() As Byte

Key = gen.GetBytes(8)
Salt = gen.Salt


I hope this helps,
Kelly